Protecting the kidney function with alkaline foods

Human kidneys are extremely hardworking. They are water filtering plants in the body that work non-stop for 24 hours a day, 365 days a year to help the body to remove metabolic waste and regulate the amount and composition of body fluids. The kidneys also help to maintain the acid-base balance of the blood and body fluids to the slightly alkaline (basis) level of pH 7.4. Other major functions of the kidney include regulating blood pressure, controlling red blood cell production, and stimulating calcium absorption by the intestine [1]. Hence, kidney function plays a vital role in maintaining the homeostasis (i.e. balance) of the body and any damage to the kidney can have serious repercussion to the whole body.

2610 The Kidney

To ensure continuous functioning, the kidney is designed to be highly resilient from the engineering design point of view. It is a redundant system with each human having a pair of kidneys, while only one is needed for us to stay healthy. Furthermore, each kidney is consisting of over a million nephrons, which are microscopic functional units of the kidneys. When some of the nephrons are damaged, the remaining nephrons are known to be able to work extra hard to compensate for the loss and sustain normal kidney function. Normal kidney function can still be sustained even up to half of the nephron mass is being injured or non-functional [2].

Chronic Kidney Disease (CKD)

Regardless of how resilient the kidney function is, it will start to snap after running on hyper drive for too long. This happens when more than 50% of the nephron mass are permanently lost. The remaining nephrons’ attempt to compensate can lead to further injury of the remaining nephrons. This will eventually cause the decrease in the kidney function, measured by the glomerular filtration rate (GFR). Normal GFR in young, healthy adults is about 125 mL/min (per 1.73m2). In most cases, the decrease in GFR is without any obvious symptoms until the GFR falls below 30 mL/min (per 1.73m2) or less than 25% normal. At which stage,  the kidneys become severely damaged and required renal specialist treatment [3]. The progressive decline in kidney function is recognised medically as chronic kidney disease (CKD). Since the decline in kidney function in the early stages is normally symptom free, a lot of people are unaware of it unless they undergo health screening.

The following table shows the stages of CKD based on the GFR.

Table 1 Staging of Chronic Kidney Disease
Stage GFR Description
1 >90 High and optimal, No CKD
2 60-89 Mild kidney damage
3a 45-59 Mild to moderate kidney damage
3b 30-44 Moderate to severe kidney damage
4 15-29 Severe kidney damage
5 less than 15 Kidney failure

Diet and CKD

The decline in kidney function can be due to the natural aging process or disease conditions, including hypertension, diabetes, other cardiovascular diseases, and obesity [3]; Regardless of the original cause, dietary factors, especially the consumption of animal protein, can greatly influence the progression of CKD [4].  In the Nurses’ Health Study, protein intake was compared to the change in estimated GFR over an 11-year span in individuals with pre-existing renal disease; analysis of the results shows that the increased consumption of animal protein is associated with the decline in GFR. This implies that consumption of animal protein plays a role in the progressive loss of kidney function [4].  Therefore, CKD patients are generally advised to limit the intake of protein, especially animal protein. A vegan/vegetarian diet is now being recommended in the Europe for CKD patients to achieve a low protein intake [5].

Legumes are excellent sources of plant-based protein. Take in moderation.
Legumes are excellent sources of plant-based protein. Take in moderation.

A diet that is high in animal protein is also high in dietary acid load. That is, it increases the amount of nonvolatile acid generated within that body. The excess nonvolatile acid must be excreted by the kidney in the form of ammonium and titratable acid in order to maintain the body’s acid-base balance. This process also can also promote kidney injury [6]. In addition, high dietary acid load also consistently leads to a state of subclinical acidosis with the body. The bicarbonate buffer of the body is constantly being depleted. In order to maintain the acid-base balance, calcium has to be drawn from the bones [6]. This process weakening the bones and the muscle in the long run, leading to muscle wasting and osteoporosis, two common conditions among CKD patients. The relationship between high dietary acid load and CKD has also been confirmed through a study using the National Health and Nutrition Examination Survey among 12,293 U.S. adult participants aged >20 years. It was found that higher dietary acid load is associated with albuminuria and low estimated GFR among the participants [7]. Therefore, a dietary target for CKD patient should be to lower the acid load in the diet to slow the progression of CKD. This can be effectively achieved through increasing the consumption of fruits and vegetables [6]. Figure 1 shows a selected type of foods and their acid load. Supplementation with sodium bicarbonate has also been shown to be a useful approach to improve  acid-base balance in CKD patients and prevent the progressive loss of renal function [8].

Figure 1 Estimated acid-producing potential of selected foods (from Scialla and Anderson (2013))
Figure 1 Estimated acid-producing potential of selected foods (from Scialla and Anderson (2013) [6])

Recommendations for Mild to Moderate CKD patients

Dietary modification and supplementation can play an important role in preventing the progression of CKD, especially during early stages.

Dietary recommendation

  • Significantly reduce the consumption of animal protein, moderately consume plant-based protein.
  • Increase consumption of fresh vegetables and fruits (alkaline foods)
  • Reduce intake of salt (prevent hypertension)
  • Reduce intake of sugar (prevent diabetes)

For patients who are not able to increase their consumption of fruits and vegetables significantly, such as aging patients with no appetite, or busy workers who eat often, dietary supplementation should be considered. The overall strategy is to support the body to be more alkaline.

Supplementation suggestion

  • High quality super greens capsules or powder (e.g. SevenPoint2 Green Caps)
  • High antioxidant juice or berries extracts, e.g. (e.g. Young Living NingXia Red)
  • Alkalising salt with sodium bicarbonate base (e.g. SevenPoint2 Alkaline Booster, or Young Living Alkalime)
  • Vitamin B Complex
  • Vitamin D (protect the bone)
Fruits are high in antioxidants and can help to protect the kidneys
Fruits are high in antioxidants and can help to protect the kidneys

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